This invention relates to an improved process for coating seeds and to an improved seed coating composition.
Some seeds lend themselves readily to the seedtaping process while others do not. Some of those not readily adaptable to seed taping are such seeds as celery, carrots, beets, and chard, all of which have irregular surfaces which create problems in the seed singulators and dispensers. Celery seeds, a particularly difficult type of seed to apply to seed tape, have a series of projecting ribs with recesses in between them that make it difficult to pick up and carry such seed by vacuum. Beet seed looks somewhat like the surface of the moon, with irregularities scattered all over. In all instances, gross irregularities do create difficulties.
Application Ser. No. 463,530 filed Apr. 24, 1974 by Peter J. Compton et al (now U.S. Pat. 3,893,258) is based on a discovery that such seed, and particularly celery seed, can be rendered suitable for seed taping by thinly coating it, the coating filling the recesses in between the ribs up to about the level of the ribs but not coating all of the ribs. The present invention relates to improvements in that type of coating,--in other words, a coating which is thin and which fills the surface irregularities but does not go beyond filling them. Too thick a coating may interfere somewhat with germination, it also consumes unnecessary material; further, it may make the seed too bulky for proper use in the seed tape.
The present invention is directed to the problem of obtaining a satisfactory coating of this thin type. Previous methods of coating celery seed left a powdery surface which gave poor results in a taping machine. Not only that, the coating tended to disintegrate when subjected to agitation, as while being fed into the seed tray or while moving in the seed tray of the seed-taping machine. The result was to leave only partially coated seed in the tray and to cause an extensive amount of dust particles to spread over the work area of the machine. Since so many of the seeds remained with fractured coatings and therefore with parts that were no longer coated, and since the nozzles which picked up the seeds could pick them up only where the nozzles engaged a smooth coat portion, this has meant that about 15% of the time the pickup nozzles failed to deliver seeds to the seed tape, and many spaces were left where seeds should have been. Inaccuracies of this order are undesirable.
Among the objects of the present invention are the provision of a new seed-coating composition and the provision of a new seed-coating method which ensures that the coating will stay on these difficult-to-handle, irregularly surfaced seeds and which therefore result in a much smaller error in seed taping. I have found that with my new coating it is possible to reduce errors (seed omissions) of these difficult-to-handle seeds below 5 percent, to eliminate the nuisance of dust, and to obtain generally improved results.